Question

You wish to measure the iron content of the well water on the new property you are about to buy. You prepare a reference standard Fe3+ solution with a concentration of 5.18×10−4 M. You treat 11.0 mL of this reference with HNO3 and excess KSCN to form a red complex and dilute the reference to 55.0 mL. The diluted reference is placed in a cell with a 1.00‑cm light path. You then take 25.0 mL of the well water, treat with HNO3 and excess KSCN, and dilute to 100.0 mL. This diluted sample is placed in a variable pathlength cell. The absorbance of the reference and the sample solutions match when the pathlength is 3.57 cm. What is the concentration of iron in the well water? For each solution, the zero is set with a blank.

Answer 1

To determine the concentration of iron in well water, a standard Fe3+ solution is prepared and its absorbance is measured. By comparing the absorbance of the well water sample with the standard, the concentration of iron in the well water can be determined.

Step-by-step explanation:

To determine the concentration of iron in the well water, a reference standard Fe3+ solution with a concentration of 5.18×10−4 M is prepared. It is then treated with HNO3 and excess KSCN to form a red complex and diluted to 55.0 mL. The diluted reference is placed in a cell with a 1.00-cm light path. Next, 25.0 mL of the well water is treated with HNO3 and excess KSCN, diluted to 100.0 mL, and placed in a variable path length cell. The absorbance of the reference and sample solutions match when the path length is 3.57 cm. By using the Beer-Lambert Law, a relationship between concentration, path length, and absorbance, we can determine the concentration of iron in the well water.